Structural characterization of the Salmonella typhimurium LT2 umu operon

Journal Article · Sat Sep 01 00:00:00 EDT 1990 · Journal of Bacteriology; (USA)

OSTI ID:6509521

Thomas, S M; Crowne, H M; Pidsley, S C; Sedgwick, S G ^[1]

---

1. National Institute for Medical Research, Mill Hill, London (England)

The umuDC operon of Escherichia coli encodes functions required for mutagenesis induced by radiation and a wide variety of chemicals. The closely related organism Salmonella typhimurium is markedly less mutable than E. coli, but a umu homolog has recently been identified and cloned from the LT2 subline. In this study the nucleotide sequence and structure of the S. typhimurium LT2 umu operon have been determined and its gene products have been identified so that the molecular basis of umu activity might be understood more fully. S. typhimurium LT2 umu consists of a smaller 417-base-pair (bp) umuD gene ending 2 bp upstream of a larger 1,266-bp umuC gene. The only apparent structural difference between the two operons is the lack of gene overlap. An SOS box identical to that found in E. coli is present in the promoter region upstream of umuD. The calculated molecular masses of the umuD and umuC gene products were 15.3 and 47.8 kilodaltons, respectively, which agree with figures determined by transpositional disruption and maxicell analysis. The S. typhimurium and E. coli umuD sequences were 68% homologous and encoded products with 71% amino acid identity; the umuC sequences were 71% homologous and encoded products with 83% amino acid identity. Furthermore, the potential UmuD cleavage site and associated catalytic sites could be identified. Thus the very different mutagenic responses of S. typhimurium LT2 and E. coli cannot be accounted for by gross differences in operon structure or gene products. Rather, the ability of the cloned S. typhimurium umuD gene to give stronger complementation of E. coli umuD77 mutants in the absence of a functional umuC gene suggests that Salmonella UmuC protein normally constrains UmuD protein activity.

• OSTI ID: 6509521
• Journal Information: Journal of Bacteriology; (USA), Vol. 172:9; Other Information: Databank sent to: GENBANK/M35010; ISSN 0021-9193
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
GENE OPERONS
MOLECULAR STRUCTURE
MUTATIONS
RADIOINDUCTION
AMINO ACID SEQUENCE
CLONING
DNA REPAIR
ESCHERICHIA COLI
GENETIC RADIATION EFFECTS
GENOTYPE
MUTAGENESIS
PLASMIDS
SALMONELLA TYPHIMURIUM
ULTRAVIOLET RADIATION
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL CONSTITUENTS
ELECTROMAGNETIC RADIATION
GENETIC EFFECTS
MICROORGANISMS
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
SALMONELLA
560130* - Radiation Effects on Microorganisms